This is the operation:

1. add 5 users( user01,user02,user03,user04,user05 ).
2. set quota for them.
3. write some data with these users.
4. delete user02 and user04
5. repquota -av
*** Report for user quotas on device /dev/sdc
Block grace time: 7days; Inode grace time: 7days
Block limits File limits
User used soft hard grace used soft hard grace
----------------------------------------------------------------------
user01 -- 1456 1024000 0 5 0 0
user03 -- 1456 1024000 0 5 0 0
user04 -- 1456 1024000 0 5 0 0
#501 -- 1456 1024000 0 5 0 0
#503 -- 1456 1024000 0 5 0 0

How to clean these records like #501 and #503 ?
Please help me. Many thanks.